The draws of the S71 Bridge, mile 0.8, and the Railroad Bridge, mile 0.9, both at Avon, operate as follows:

(a) The bridges operate as one unit. The owners shall provide signal systems so connected that the operator of either bridge may simultaneously notify the operator of the other bridge. The operator of the first bridge to be passed shall be responsible for observing the approach vessels, for receiving and acknowledging signals, and for coordinating the opening of the other draw.

(b) The draws shall open on signal; except that, from May 15 through September 30 from 4 p.m. to 7 p.m. Monday through Friday except Federal holidays and from 9 a.m. to 9 p.m. Saturdays, Sundays, and holidays, the draw need be opened only on the hour and half hour if a vessel is waiting to pass.

(c) The owners of the bridges shall provide and keep in good legible condition two board gages painted white with black figures not less than eight inches high to indicate the vertical clearance under the closed draw at all stages of the tide. The gages shall be so placed on the bridges that they are plainly visible to operators of vessels approaching the bridges either up or downstream.